The music industry produces audio content at various loudness levels. This lack of an established standard during production provides a poor user experience when randomly playing back content produced by different entities, produced for different albums, and/or content of different genres as loudness levels may wildly fluctuate.
The movie industry widely adopted a loudness normalization scheme based on the loudness of dialog anchors in a movie.1 Further, the International Telecommunication Union Radiocommunication (ITU-R) Sector ratified loudness normalization recommendations based on program loudness.2 The result is that all content in movies is at a static target loudness level after normalization. This approach reduces the need for a user to adjust volume settings triggered by inconsistent loudness variations from one audio track to another. ATSC, “ATSC Standard: Digital Audio Compression (AC-3, E-AC-3),” Doc. A/52:2012 23 Mar. 2012.2ITU-R, “Algorithms to measure audio programme and true-peak audio level,” Recommendation ITU-R BS.1770-3, August 2012.
While loudness normalization is a first step in the right direction, it still results in undesired and sometimes unexpected loudness levels. This is because the assumption that all content should play at the same static target loudness is not always correct.